Holocene ice-stream shutdown and drainage basin reconfiguration in northeast Greenland

Franke, Steven; Bons, Paul D.; Westhoff, Julien; Weikusat, Ilka; Binder, Tobias; Streng, Kyra; Steinhage, Daniel; Helm, Veit; Eisen, Olaf; Paden, John; Eagles, Graeme; Jansen, Daniela

doi:10.1038/s41561-022-01082-2

Cited by 18 publications

(30 citation statements)

References 53 publications

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“…5). Englacial layers at the onset of enhanced flow (>15 ma -1 ) undulate in distinct trough and crest sequences, similar to folds observed elsewhere in Antarctica and Greenland (Bell et al, 1998;Conway et al, 2002;Ng et al, 2004;Holschuh et al, 2014;Franke et al, 2022a).…”

Section: Englacial Foldingsupporting

confidence: 66%

“…The large-scale englacial folding we observe at the shear margin is therefore likely to be a result of lateral convergence, driven by enhanced ice flow through the subglacial valley (Franke et al, 2022a). However, we note that the englacial architecture of Lambert Glacier appears to be sensitive to variations in basal thermal conditions; where it is likely that ice compression causing the fold is exaggerated by the transition from cold/frozen conditions outside the shear margin to the warm/ thawed conditions in the central trunk.…”

Section: Englacial Structure Of Lambert Glacier Shear Marginmentioning

confidence: 85%

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Englacial Architecture of Lambert Glacier, East Antarctica

Sanderson

Winter

Callard

et al. 2023

Preprint

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Abstract. The analysis of englacial layers using radio-echo sounding data enables the characterisation and reconstruction of current and past ice-sheet flow. Despite the Lambert Glacier catchment being one of the largest in Antarctica, discharging ~16 % of East Antarctica’s ice, its englacial architecture has been little analysed. Here, we present a comprehensive analysis of Lambert Glacier’s englacial architecture using radio-echo sounding data collected by the Antarctica's Gamburtsev Province Project (AGAP) North survey. We used an “internal-layering continuity index” (ILCI) to characterise the internal architecture of the ice and identify four macro-scale ILCI zones with distinct glaciological contexts. Whilst the catchment is dominated by continuous englacial layering, disrupted or discontinuous layering is highlighted by the ILCI at both the onset of enhanced ice flow (defined here as >15 ma−1) and along the shear margin, revealing the transition from internal-deformation-controlled to basal-sliding-dominated ice flow. These zones are characterised by buckled and folded englacial layers which align with the current ice-flow regime, and which we interpret as evidence that the flow direction of the Lambert Glacier trunk has changed little, if at all, during the Holocene. However, disturbed englacial layers along a deep subglacial channel that does not correspond to modern ice-flow routing suggest that ice-flow change has occurred in a former tributary which fed Lambert Glacier from grid north. As large outlet systems such as Lambert Glacier are likely to play a vital role in the future drainage of the East Antarctic Ice Sheet, constraining their englacial architecture to reconstruct their past ice flow and assess basal conditions is important.

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Section: Englacial Foldingsupporting

confidence: 66%

Section: Englacial Structure Of Lambert Glacier Shear Marginmentioning

confidence: 85%

Englacial Architecture of Lambert Glacier, East Antarctica

Sanderson

Winter

Callard

et al. 2023

Preprint

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“…Furthermore, we have assumed that the ice stream remains constant over time. Franke et al (2022) however suggest the NEGIS (the ice stream EGRIP is within) has shifted during the Holocene (within the last 11,700 years).…”

Section: Timescales For Fabrics To Adjust To New Deformationsmentioning

confidence: 95%

Bridging the Gap Between Experimental and Natural Fabrics: Modeling Ice Stream Fabric Evolution and its Comparison With Ice‐Core Data

Richards,

Pegler,

Piazolo

et al. 2023

JGR Solid Earth

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Fabrics, also known as textures or crystallographic preferred orientations, reveal information about the deformation history of the flow of polycrystalline materials, including glacial ice, olivine in the mantle, and feldspar and quartz in the crust. Ice fabrics can have an order‐of‐magnitude effect on the ease of flow in ice sheets. However, due to the choice of ice core drill site locations, the outputs of fabric models have mostly been compared to observations from the least dynamic regions of the ice sheet (ice divides). Recently, fabric data from an active ice stream have become available from ice cores drilled at the East Greenland Ice‐core Project (EGRIP). In this work, we present a novel approach that combines satellite‐derived velocity data with the fabric evolution model SpecCAF, a continuum model based on dominant dislocation creep. We directly compare model output to ice‐core observations from EGRIP, allowing us to examine the quantitative predictions of calibrated fabric models alongside those of active ice streams for the first time. As the model is calibrated against laboratory experiments, it provides a surrogate to compare the evolution of fabrics under laboratory and natural conditions. The predictions show good qualitative agreement with the observed fabric patterns and orientations, suggesting that a fabric between a girdle and horizontal maximum, orientated perpendicular to the flow direction, is the characteristic ice stream fabric. A discrepancy in fabric strength is attributed to the lower strain rates of ice sheets compared to laboratory experiments, revealing a significant strain‐rate dependence in the processes controlling fabric evolution.

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“…Ice streams are the primary source of dynamic ice mass loss and are hence of great importance in the stability of ice sheets 11 – 13 . Accordingly, it is crucial to accurately reproduce ice stream dynamics in prognostic ice-sheet models to reduce uncertainties in estimates of future ice-sheet evolution and sea-level rise.…”

Section: Introductionmentioning

confidence: 99%

Crystal orientation fabric anisotropy causes directional hardening of the Northeast Greenland Ice Stream

et al. 2023

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The dynamic mass loss of ice sheets constitutes one of the biggest uncertainties in projections of ice-sheet evolution. One central, understudied aspect of ice flow is how the bulk orientation of the crystal orientation fabric translates to the mechanical anisotropy of ice. Here we show the spatial distribution of the depth-averaged horizontal anisotropy and corresponding directional flow-enhancement factors covering a large area of the Northeast Greenland Ice Stream onset. Our results are based on airborne and ground-based radar surveys, ice-core observations, and numerical ice-flow modelling. They show a strong spatial variability of the horizontal anisotropy and a rapid crystal reorganisation on the order of hundreds of years coinciding with the ice-stream geometry. Compared to isotropic ice, parts of the ice stream are found to be more than one order of magnitude harder for along-flow extension/compression while the shear margins are potentially softened by a factor of two for horizontal-shear deformation.

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Holocene ice-stream shutdown and drainage basin reconfiguration in northeast Greenland

Cited by 18 publications

References 53 publications

Englacial Architecture of Lambert Glacier, East Antarctica

Englacial Architecture of Lambert Glacier, East Antarctica

Bridging the Gap Between Experimental and Natural Fabrics: Modeling Ice Stream Fabric Evolution and its Comparison With Ice‐Core Data

Crystal orientation fabric anisotropy causes directional hardening of the Northeast Greenland Ice Stream

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